When almost every pet house cat has been neutered—a situation that already applies in some parts of the UK—then we must fear for the next generations of cats. These will then mainly be the offspring of those that live on the fringes of human society—feral males, stray females, as well as those female cats owned by people who either do not care whether their cat is neutered or not, or have a moral objection to neutering…

The only significant difference between such a hypothetical parasite and neutering is that the latter does not require a host (a cat) to continue: it lives as an idea, and so is detached from its effects.16 Because neutering inevitably targets those cats that are being best cared for, it must logically hand the reproductive advantage to those cats that are least attached to people, many of which are genetically predisposed to remain unsocialized. We must consider the long-term effects of neutering carefully: for example, it might be better for the cats of the future as a whole if neutering programs were targeted more at ferals, which are both the unfriendliest cats and also those most likely to damage wildlife populations

John Bradshaw, Cat sense: how the new feline science can make you a better friend to your pet, New York, 2013, p. 305